Eric Bailey
75 lines
1.9 KiB
TypeScript
75 lines
1.9 KiB
TypeScript
export function extractDataUriMime(uri: string): string {
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return uri.substring(uri.indexOf(':') + 1, uri.indexOf(';'))
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}
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export function getResizedDimensions(
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originalDims: {
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width: number
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height: number
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},
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maxDimension: number,
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) {
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if (
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originalDims.width <= maxDimension &&
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originalDims.height <= maxDimension
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) {
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return originalDims
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}
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const ratio = Math.min(
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maxDimension / originalDims.width,
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maxDimension / originalDims.height,
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)
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return {
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width: Math.round(originalDims.width * ratio),
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height: Math.round(originalDims.height * ratio),
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}
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}
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// Fairly accurate estimate that is more performant
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// than decoding and checking length of URI
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export function getDataUriSize(uri: string): number {
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return Math.round((uri.length * 3) / 4)
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}
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export function isUriImage(uri: string): boolean {
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return /\.(jpg|jpeg|png|webp).*$/.test(uri)
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}
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export function blobToDataUri(blob: Blob): Promise<string> {
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return new Promise((resolve, reject) => {
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const reader = new FileReader()
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reader.onloadend = () => {
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if (typeof reader.result === 'string') {
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resolve(reader.result)
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} else {
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reject(new Error('Failed to read blob'))
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}
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}
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reader.onerror = reject
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reader.readAsDataURL(blob)
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})
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}
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export type ImgproxyPreset =
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| 'default'
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| 'avatar_thumbnail'
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| 'avatar'
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| 'banner'
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| 'feed_fullsize'
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| 'feed_thumbnail'
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| 'download'
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// Using capturing groups here instead of lookbehinds in order to support older versions of Safari.
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// https://bugs.webkit.org/show_bug.cgi?id=174931
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const IMGPROXY_PRESET_RE =
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/(\/img\/)(default|avatar_thumbnail|avatar|banner|feed_fullsize|feed_thumbnail|download)(\/)/
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/**
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* Replaces any imgproxy preset in a CDN URI with the given preset.
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*/
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export function convertCdnPreset(uri: string, preset: ImgproxyPreset): string {
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return uri.replace(IMGPROXY_PRESET_RE, `$1${preset}$3`)
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}
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